penis (redirected from Human dick)

penis: see reproductive system.

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penis

Male sex organ, which also provides the channel for urine to leave the body. Three long columns of tissue extend through its length, covered by elastic tissue and a thin layer of skin. One expands at the tip into a mushroom-shaped structure (glans penis) and contains the urethra (see urinary system), which ends in a slitlike opening. In sexual arousal, blood fills spaces in the tissue, and blood vessels constrict to hold it there, enlarging and hardening the penis in an erection. The foreskin, a circular fold of skin covering the glans, is often removed (see circumcision). See also reproductive system.

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penis

the male organ of copulation in higher vertebrates, also used for urine excretion in many mammals

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Penis

The male organ of copulation, or phallus. In mammals the penis consists basically of three elongated masses of erectile tissue. The central corpus spongiosum (corpus urethrae) lies ventral to the paired corpora cavernosa. The urethra runs along the underside of the spongiosum and then normally rises to open at the expanded, cone-shaped tip, the glans penis, which fits like a cap over the end of the penis. Loose skin encloses the penis and also forms the retractable foreskin, or prepuce.

Erection of the penis is caused by nervous stimulation resulting in engorgement of the spiral helicine arteries and the plentiful venous sinuses of the organ. In most mammals other than Primates the penis is retracted into a sheath when not in use.

In submammalian forms the penis is not as well developed. Crocodilians, turtles, and some birds have a penis basically like that of mammals, lying in the floor of the cloaca. When erected, it protrudes from the cloaca and functions in copulation. Other vertebrates lack a penis, although various functionally comparable organs may be developed such as the claspers on the pelvic fins of sharks and the gonopodia on the anal fins of certain teleost fishes.